The invention pertains to a transport system, in particular, a passenger transport system, such as an elevator, a moving sidewalk, or an escalator, where said transport system is provided with a controller, a drive motor, and a safety switch that is able to distinguish between a safe state of the transport system and an unsafe state of the transport system and that is connected to the controller in order to interrupt the power supply to the drive motor in the unsafe state.
Transport systems of this type are broadly utilized in the form of elevators, as well as in the form of escalators and moving sidewalks. The safety switch serves for monitoring safety-related states of the corresponding transport system. In elevator systems, for example, the elevator shaft doors and, if applicable, the elevator car doors are continuously monitored. When one of the doors is opened, the controller interrupts the power to the drive motor until the door, and thus the safety switch, are correctly closed again and power to the drive motor is restored. The doors of elevator systems require considerable maintenance. For example, the elevator shaft doors are typically suspended from suspension mechanisms on which rollers are mounted in corresponding guide rails, which are accommodated in the lintel beam over the shaft door opening. The door may comprise one or more door panels. There are door designs with centrally opening shaft doors and laterally opening shaft doors, as well as those in which several door panels open and close in telescoping fashion in only one direction. The drive of the shaft doors is realized, e.g., by means of a drive cable or drive belt that is also arranged in the lintel beam over the shaft door opening. The shaft doors must be correctly adjusted in order to ensure the reliable opening and closing of the doors. Elevator car doors are similarly arranged on elevator cars.
Currently, two-part safety contacts are used in elevator doors, where one part contains two openings that lie closely adjacent and the other part essentially consists of a U-shaped metal profile, which, when the door is correctly closed, protrudes into the two openings of the other part and closes the contact between two electrical connections therein. Here, the two parts of the safety switch are arranged on door panels that open and close relative to one another, particularly in a region above the lintel.
Alternatively, one part of the safety contact is arranged on an opening door panel in laterally opening doors, where the other part is arranged, for example, on the door frame or the door frame soffit. The door switch is adjusted in such a way that the contact is closed when the door is correctly closed. The door switch requires adjustments in order to ensure that the contact is no longer closed once there exist a certain gap, for example, between the two door panels. When this condition occurs, the power to the drive motor is interrupted and operation of the elevator system can only resume if the elevator doors are readjusted and correctly close again.
The customary wear associated with the operation as well as the use of force on the elevator door, e.g., due to forcefully opening the door, etc., causes the door no longer correctly to close. In both instances, the incorrectly or unsafely closed condition does not occur from one instant to the next, but the transition from a correctly to an incorrectly closed condition takes place gradually. Conventional safety switches are unable to detect this gradual deterioration. The safety switch is only able to detect such deterioration once a certain wear or misalignment condition appears. In such circumstances, the elevator system is deactivated from one instant to the next. Such sudden shutdowns of elevator systems are undesirable for several reasons. First, the operators of elevator systems are always unhappy if the elevator system suddenly shuts down and maintenance must be called to restore service. Second, high expenditures with respect to personnel and logistics are needed to ensure that those elevator systems requiring service can be repaired around the clock.
The situation is quite similar with respect to escalators or moving sidewalks. These passenger transport systems typically contain a so-called step band that consists of a series of interconnected step elements, i.e., stairstep or pallet elements, which are moved from an entry point to an exit point by a drive motor. So-called bottom paneling is provided to the side of the step elements or pallet elements. The gap between the step elements and the bottom paneling must be maintained within a relatively narrow range for safety reasons. This is usually also monitored with corresponding safety switches. These safety switches typically trigger when the gap is exceeded and cause the escalator or moving sidewalk to be deactivated in such cases. In principle, the negative effects of these undesirable shutdowns are identical to those described above with reference to elevator systems.
The present invention is based on the objective of making available transport systems of the initially mentioned type which fulfill the corresponding safety requirements and significantly minimize the risk of a sudden shutdown when an unsafe state is detected.
According to the invention, this objective is realized in that the safety switch is effected so that it is able also to detect a warning state in addition to the safe and unsafe states.
The invention makes it possible to detect a warning state before an unsafe state is reached. Consequently, it is possible to indicate this warning state via the safety control. A corresponding warning message may be directly sent to maintenance, e.g., via a remote line. An arbitrary display device may alternatively or additionally inform the building""s elevator attendant who then contacts maintenance. The transport system may be adjusted in such a way that, during typical operation, the warning state is indicated, for example, at least fourteen days before an unsafe state occurs. This means that sufficient time remains for readjusting the system or exchanging the defective parts during planned maintenance procedures. It would also be possible to realize the safety switch such that it continuously indicates the state of wear of the system instead of merely indicating a warning state once a certain intermediate state is reached.
Naturally, it is also possible to detect several intermediate states that essentially correspond to different warning levels. The safety switch preferably consists of a proximity switch, where an inductive proximity switch is particularly preferred. Alternatively, capacitive switches or devices may be used which, for example, determine the relevant spacing between two parts with the aid of light, ultrasound, etc.
Generally speaking, safety switches that cannot be manipulated are particularly preferred. For example, simple distance measuring devices that operate with ultrasound or light have the disadvantage that a closed door can be simulated with a mirror or another object. This is the reason why inductive proximity switches, particularly those composed of two parts are provided. In this case, the xe2x80x9cpassive partxe2x80x9d preferably consists of a magnetic material, e.g., ferrite, with a certain magnetic field strength, to which the sensor part is xe2x80x9ccalibrated.xe2x80x9d This type of switch design is difficult to manipulate with any given magnet. This feature is particularly important because elevator surfers increasingly attempt to bypass the safety devices in elevator systems in order to ride on the roof of the elevator car.
The safety switch is preferably realized in such a way that it outputs a certain non-zero value of the output variable, e.g., the voltage, the current, the resistance, etc. When using a switch that does not deliver three discrete values, but rather is able to generate individual or continuous intermediate values, a continuous range of values which should not include zero is correspondingly output as the output signal. A switch of this type which, in its normal mode, only outputs signals that have a certain predetermined value that differs from zero or signals that lie within a certain defined range of values also makes it possible to realize a plausibility check. For example, when a switch in which the voltage is used as the output variable delivers an output signal of 0 V to the controller, it can be assumed that a switch defect has occurred or that the cable connection between the switch and the controller is interrupted. Depending on the type of switch, a voltage that is significantly higher than the usual output voltage of the switch may, for example, indicate a short circuit in the switch and consequently a switch failure. This makes it possible significantly to improve the operational reliability of the system.
The controller is preferably realized such that it processes the signal of the safety switch and interrupts the power to the drive motor if an unsafe condition is detected, where the controller does not interrupt the power but generates a warning signal if an intermediate state between completely safe and unsafe is detected, where the controller does not interrupt the power and does not generate a warning signal if a safe state is detected, and where the controller determines that the safety switch is not functional and thusly interrupts the power if a voltage value is detected which does not correspond to any of the predetermined voltage values of the safety switch. A value that does not correspond to any of the predetermined values of the safety switch occurs, for example, if no signal arrives at the controller or if values that are significantly higher than the predetermined output values arrive at the controller. The controller may be correspondingly realized in the form of a hardware circuit. Alternatively, it would also be possible to realize the controller with a microprocessor in which a corresponding algorithm in the form of a data processing program is stored. This program continuously requests values to be delivered by the safety switch(es) within certain intervals.
The present invention may be utilized in connection with conventional safety chains, for example, in elevator systems. In such safety chains, the individual shaft door contacts are typically connected in series, where the power to the drive motor is interrupted if any of the shaft door contacts is opened. In this safety chain, the so-called shaft pit emergency shutdown switch and the inspection switch are arranged on the roof of the elevator car. In a series circuit of this type, it is advantageous to realize the safety switch such that an intermediate state can also be assumed by the switch at a certain predetermined resistance in addition to the open state of the switch in which the resistance is essentially infinite and the closed state of the switch in which the resistance is essentially zero. This means that the system controller receives a correspondingly reduced voltage that can be defined as a warning state. Alternatively, it would be possible to forward the warning states to the controller other than through the safety chain, i.e., through separate connections to the controller.
Generally speaking, it is particularly preferred to use the present invention in connection with modern safety systems in which the status of the various safety switches is queried individually and the status messages of the safety switches are separately forwarded to the elevator controller. One example of an elevator safety system of this type in which a bus system is used to forward the data is described in U.S. Pat. No. 6,173,814 B1.
The transport system preferably consists of an elevator, and the safety switch preferably consists of a door contact switch that detects the closed state of the door.
The transport system preferably consists of an escalator or a moving sidewalk with a driven step band and a bottom paneling, where the safety switch monitors the gap between the step band and the bottom paneling.